Methods and systems to accurately display lateral deviation symbology in offset approaches to runways

ABSTRACT

Systems and methods to accurately display lateral deviation symbology in offset approaches to runways is provided. A system for on-aircraft display of lateral deviation symbology for use in offset approaches comprises means for generating a conformal video display representation of an aircraft&#39;s current position, means for notifying a flight crew of the existence of an offset approach, means for displaying an extended runway center line, and means for displaying an approach line.

TECHNICAL FIELD

The present invention generally relates to aircraft navigationinstrumentation and more specifically to displaying lateral deviationsymbology.

BACKGROUND

The primary approach system used by most airports is the InstrumentLanding System (ILS). ILS facilities provide an accurate and dependablemeans of navigating an aircraft to most runways for landing. An ILStransmits narrow horizontal beams which let flight crews know if theiraircraft is left, right, or directly on course for a runway. The signaltransmitted by the ILS consists of two vertical fan-shaped beam patternsthat overlap at the center. Ideally, the beams are aligned with theextended centerline of the runway. The right side beam is typicallyreferred to as the “blue” area while the left side of beam is the“yellow” area. An overlap between the two beams provides an on-tracksignal to aircraft. Ideally, at the point where ILS receivers on theaircraft receive blue area and yellow area beams signals of equalintensity, the aircraft is located precisely on the approach track ofthe runway centerline.

Due to the presence of terrain, physical obstacles, or politicalsituations, some approaches to runways are guided by an ILS with a beamdirection not aligned with the runway centerline direction. Whenexecuting such a runway approach, flight crews must follow the ILS beamsto a point, but then turn the aircraft to the true runway direction forfinal landing.

This misalignment between the runway centerline direction and the ILSapproach line direction creates difficulties when displaying informationfor such an approach on high resolution symbolic visual display systems,such as conformal perspective view visual displays, because publishedbearing numbers and ILS signals for the runway may not providesufficient accuracy and resolution to properly display the approach lineover an extended range. Additionally, flight crews must be made aware ofthe existence of the offset approach, and on the whereabouts of thetransition point in order to deviate from the ILS approach line and turnthe aircraft towards the runway direction.

For the reasons stated above and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the specification, there is a need in the art for systemsand methods to accurately display lateral deviation symbology in offsetILS approaches.

SUMMARY

The Embodiments of the present invention provide methods and systems forto accurately display lateral deviation symbology in offset approachesand will be understood by reading and studying the followingspecification.

In one embodiment, a graphical display system for an aircraft isprovided. The system comprises a processor adapted to perform real-timecomputations necessary for generating graphical representations of theaircraft's position, wherein the processor is further adapted togenerate a first lateral deviation symbology representing the aircraft'scurrent position with respect to an approach line, and generate a secondlateral deviation symbology representing the aircrafts current positionwith respect to an extended runway center line. The system furthercomprises a runway assistance landing system receiver coupled to theprocessor, the runway assistance landing system receiver adapted toreceive signals for the processor transmitted by an airport runwayassistance landing system; one or more aircraft position sensors coupledto the processor, the sensors adapted to detect the position of theaircraft; and a display coupled to the processor, the display adapted todisplay the graphical representations generated by the processor.

In another embodiment, a system for on-aircraft display of lateraldeviation symbology for use in offset approaches is provided. The systemcomprises means for generating a conformal video display representationof an aircraft's current position; means for notifying a flight crew ofthe existence of an offset approach; means for displaying an extendedrunway center line; and means for displaying an approach line.

In yet another embodiment, a method for landing an aircraft at anairport runway having an offset approach is provided. The methodcomprises aligning a first conformal lateral deviation symbology with anapproach line during an approach prior to reaching a transition point;turning the aircraft upon reaching the transition point; and aligning asecond conformal lateral deviation symbology with an extended runwaycenter line during an approach after reaching the transition point.

In still another embodiment, a computer-readable medium havingcomputer-executable program instructions for a method for displayinglateral deviation symbology in offset approaches is provided. The methodcomprises notifying a flight crew of the existence of an offsetapproach; displaying an extended runway center line; and displaying anapproach line.

DRAWINGS

The present invention can be more easily understood and furtheradvantages and uses thereof more readily apparent, when considered inview of the description of the preferred embodiments and the followingfigures in which:

FIG. 1 is a block diagram illustrating a graphical display system of oneembodiment of the present invention;

FIG. 2 is a diagram illustrating a conformal perspective view display ofan offset approach of one embodiment of the present invention;

FIG. 3 is a diagram illustrating an offset approach runway facility ofone embodiment of the present invention;

FIG. 4 is a diagram illustrating a conformal perspective view display ofan offset approach after arriving at the transition point, of oneembodiment of the present invention;

FIG. 5 is a flow chart illustrating a method for displaying lateraldeviation symbology in offset ILS approaches, of one embodiment of thepresent invention; and

FIG. 6 is a flow chart illustrating a method for landing an aircraft atan airport runway having an offset ILS approach, of one embodiment ofthe present invention.

In accordance with common practice, the various described features arenot drawn to scale but are drawn to emphasize features relevant to thepresent invention. Reference characters denote like elements throughoutfigures and text.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific illustrative embodiments in which theinvention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention, and it is to be understood that other embodiments may beutilized and that logical, mechanical and electrical changes may be madewithout departing from the scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense.

Although the examples of embodiments in this specification are describedin terms of the currently widely used ILS, embodiments of the presentinvention are not limited to applications of airports utilizing ILS. Tothe contrary, embodiments of the present invention are applicable to anyrunway utilizing a runway assistance landing system (of which ILS is anexample) that transmits a signal to aircraft indicating an approach lineto a runway that is offset from the runway's true centerline. Alternateembodiments of the present invention to those described below mayutilize whatever runway assistance landing system signals are availableto dynamically calibrate and determine a precise approach course to arunway and display the approach course relative to the runway centerlinedirection to pilots.

FIG. 1 illustrates a system 100 for accurately displaying lateraldeviation symbology in offset ILS approaches of one embodiment of thepresent invention. System 100 comprises a display 120 adapted fordisplaying symbolic representations of data, such as, but not limited toaircraft, terrain, and runway position information generated byprocessor 130. In one embodiment, system 100 is a Honeywell PRIMUS EPICintegrated avionics systems wherein processor 130 is a graphic displaygeneration computer, such as the Honeywell Advanced Graphics Moduleembedded within the Honeywell PRIMUS EPIC system. In one embodiment,display 120 is a head-down display, such as a flat panel video display.In other embodiments, display 120 is a head-up display (HUD) adapted toproject information into a pilot's field of vision.

System 100 addresses the problems with accurately displaying lateraldeviation symbology for offset runway approaches by providing anaircraft flight crew graphical representations of both the ILS approachline for a runway and the runway's centerline together with a graphicalrepresentation of the aircraft's location with respect to the ILSapproach line and the runway's centerline. Additionally, system 100graphically illustrates for the flight crew the point where the aircraftshould stop following the ILS approach line, and start aligning with therunway's centerline for landing.

Processor 130 is adapted to perform real-time computations necessary forgenerating conformal perspective view graphical representations of anaircraft's position with respect to other objects of interest. As usedin this application, a conformal video display is characterized ashaving the ability to present information using a set of symbols thatare conformal with the outside environment (e.g. having perspective,proportions and relationships that are true to reality.) Processor 130is connected to flight management systems (FMS) 150 for obtainingaircraft parameters such as aircraft position and attitude. In oneembodiment, FMS 150 obtains aircraft position and attitude from sensorssuch as GPS sensor 152 and inertial navigation system (INS) 154. FMS 150further comprises one or more flight management system databases 140adapted to provide processor 130 with data necessary to generateaccurate graphical representations of one or more of airport runways,airport runway centerlines, and ILS beacon positions. In one embodiment,processor 130 is adapted to uplink data necessary to generate accurategraphical representations of one or more of airport runways, airportrunway centerlines, and ILS beacon positions. Processor 130 is alsoconnected to ILS receiver 160 for receiving ILS signals transmitted byairport ILS systems. System 100 includes terrain data base 145 which isadapted to provide processor 130 with data necessary to generateaccurate graphical representations of the terrain in the proximity ofthe aircraft.

FIG. 2 illustrates a conformal 3D perspective view 200 provided bydisplay 120 to a flight crew as their aircraft prepares to land at anairport runway 205 having an offset approach. For an offset approachrunway, processor 130 notifies the flight crew of the existence of theoffset approach by generating both an extended runway centerline 210 andan ILS approach line 220 on display 120. In one embodiment, extendedrunway centerline 210 and ILS approach line 220 are displayed such thatthey are easily discemable from each other (e.g. differing colors, linethicknesses, solid lines verses dashed lines). Information provided to aflight crew by view 200 of one embodiment of the present inventionincludes the existence of the offset approach, visual display of thetrue runway centerline, and a visual indication of the degree of theoffset between the ILS approach and the true runway centerline.

View 200 further visually provides the flight crew with the location oftransition point 230, where the aircraft must turn to align itself withrunway 205 for landing. Transition point 230 indicates the point whereextended runway centerline 210 and ILS approach line 220 intersect. Asan aircraft initially approaches runway 205 for landing, the flight crewfollows ILS approach line 220 until the aircraft reaches transitionpoint 230. Upon reaching transition point 230, the flight crew adjuststhe flight path of the aircraft to align the aircraft with extendedrunway center line 210 to complete the approach to runway 205. In oneembodiment, ILS approach line 220 is terminated at the point ofintercepting extended runway centerline 210 to indicate transition point230.

The ILS approach line 220 is determined by using one or more positionpoints derived from ILS signals received by ILS receiver 160, and fromrunway configuration data, to provide a real-time direction calibration,which ensures its accurate positioning and orientation on conformalperspective visual display 120. In one embodiment, upon receiving datafrom an ILS signal from an airport, processor 130 performs a calibrationprior to displaying ILS approach line 220. Calibrating ILS approach line220 with respect to the intended landing target ensures the correctpositioning of ILS approach line 220 on display 120. In straight-innon-offset approaches, such calibration is not needed as the runway enddata points are sufficiently accurate to align the approach line andrunway center line. The spatial position and orientation of ILS approachline 220 is determined and calibrated by using ILS signals received,relative to current aircraft position, runway position, and ILS beaconpositions. The calibration is conducted at a distance from the runwaywhere a sufficient and valid ILS signal is received. In one embodiment,processor 130 determines whether the ILS signal strength meets asufficient threshold to provide reliable guidance data. Processor 130then correlates the aircraft's current location (e.g. as determined byone or more of onboard GPS sensors 152 and inertial navigation system(INS) sensors 154) and runway 205 location data to compute where theaircraft is in relation to runway 205, and to compute the lateraldeviation between the aircraft's current flight path and ILS approachline 220. A zero lateral deviation corresponds to a position on theapproach line. Non-zero deviations correspond to positions having aknown angle with respect to the approach line as measured from a lateraldeviation source point. Processor 130 then generates the spatialposition and orientation of the approach line and conformal lateraldeviation symbology 240 with respect to the approach line, whichdisplays to the flight crew the deviation between the aircrafts currentposition (indicated by aircraft symbol 242) and ILS approach line 220.

FIG. 3 illustrates an example of a runway 305 having an approach line320 offset from the runway centerline 310 due to terrain 340 surroundingrunway 305. In one embodiment, runway location data used by processor130 to generate extended runway centerline 210 includes coordinates fora runway beginning center point 306 and a runway end center point 307.In one embodiment, the runway end location data includes the longitudeand latitude coordinates of center points 306 and 307. In oneembodiment, processor 130 calculates centerline 310 based on a line thatintersects runway beginning center point 306 and runway end center point307 in order to generate and display extended runway centerline 210. Inone embodiment, runway end location data for runway 305 is residentwithin one or more FMS databases 140. In one embodiment, runway endlocation data for runway 305 is uplinked to processor 130 by one or moretransmitters 330 local to runway 305.

FIG. 4 illustrates a conformal 3D perspective view 400 provided bydisplay 120 to a flight crew approaching runway 205 for landing, aftertheir aircraft reaches transition point 230. When the aircraft positionreaches transition point 230, ILS approach line 220 no longer providesvalid guidance for landing on runway 205. The flight crew must align theaircraft with the extended runway center line 210 to correctly land theaircraft. In one embodiment, when processor 130 determines that theaircraft has reached transition point 230, processor 130 stopsdisplaying ILS approach line 220. Processor 130 then shifts tocorrelating the aircraft's current location, as provided by FMS 150,with runway 205 location data, in order to compute where the aircraft isin relation to runway 205, and to compute the lateral deviation betweenthe aircrafts current flight path and extended runway center line 210.Processor 130 generates conformal lateral deviation symbology 440 whichdisplays to the flight crew the deviation between the aircrafts currentposition (indicated by aircraft symbol 442) and the extended runwaycenter line 210. In one embodiment, processor 130 differentiates theappearance of conformal lateral deviation symbology 440 from conformallateral deviation symbology 240 (e.g. by changing the color or shape ofthe symbology) in order to indicate to the flight crew that display 120is now displaying conformal position approach information as determinedby FMS 150 rather than ILS signals.

In one embodiment, processor 130 displays offset approach information(e.g. display both an ILS approach line 220 and a separate extendedrunway centerline 210) only for airport runways having an offsetapproach. In one embodiment processor 130 detects whether a given runwaypossess an offset approach by comparing runway direction data from FMSdatabase 140 for that runway with the approach line direction providedby that runway's ILS signals. As would be appreciated by one skilled inthe field of aviation, there is sometimes a normal, nominal offsetbetween the runway centerline direction and the approach line directionprovided by ILS signals. Nominal offsets for a given runway may varywith time over the course of a year, or shift due to changes in theEarth's magnetic field. Therefore, in one embodiment, processor 130 isadapted to display offset approach information when it detects an offsetin excess of a threshold offset which is based on an expected nominaloffset. In one embodiment processor 130 determines whether a givenrunway possess an offset approach by evaluating runway direction datauplinked to processor 130 by one or more transmitters 330 local torunway 305. In one embodiment, runway direction data includes, but isnot limited to, the position, elevation and bearing of the runway, andILS beam orientation. Additionally some flight crew pilots possesssufficient experience to know when certain airport runways have offsetapproaches. Accordingly, in one embodiment, processor 130 is adapted toallow the pilot to manually activate the offset approach displayfunctions describe in regards to FIGS. 2 and 4 above.

FIG. 5 illustrates a method 500 for displaying lateral deviationsymbology in offset ILS approaches, of one embodiment of the presentinvention. The method comprises displaying an extended runway centerline (520) and displaying an ILS approach line (530). Displaying both anextended runway centerline and an ILS approach line notifies the flightcrew of the existence of the offset approach, informs a flight crew ofthe true runway centerline, and illustrates the degree of the offsetbetween the ILS approach and the true runway centerline. Further, thepoint where the extended runway centerline and the ILS approach lineintersect provides the flight crew with the location of the transitionpoint, where the aircraft should stop following the ILS approach line,and start following the extended runway centerline to land the aircraft.In one embodiment, the method further comprises displaying a firstconformal lateral deviation symbology with respect to the ILS approachline (540) as an aircraft is approach a transition point, and displayinga second conformal lateral deviation symbology with respect to theextended runway center line (550) after the aircraft has reached thetransition point. The first and second conformal lateral deviationsymbology, indicate to the pilot the degree of the aircraft's lateraldeviation from the ILS approach line and the extended runway centerline,respectively. In one embodiment, the first conformal lateral deviationsymbology is distinguishable from the second conformal lateral deviationsymbology. In one embodiment, the first conformal lateral deviationsymbology is differentiated from the second conformal lateral deviationsymbology by one or more of a different color, a different linethickness, or a different line style. Additionally the extended runwaycenter line may be a different color from the ILS approach line. In oneembodiment, the transition point is indicated by ending the ILS approachline at a point where the ILS approach line intersects the extendedrunway center line (560). Additionally, after the aircraft has reachedthe transition point, in one embodiment the method further comprisesceasing the display of the ILS approach line during and approach afterreaching a transition point (570).

FIG. 6 illustrates a method 600 for landing an aircraft at an airportrunway having an offset ILS approach. The method comprises aligning afirst conformal lateral deviation symbology with an ILS approach lineduring an approach prior to reaching a transition point (610). Aspreviously discussed, the first conformal lateral deviation symbologyindicates to the pilot the degree of the aircraft's lateral deviationfrom the ILS approach line. The pilot maneuvers the aircraft's flightcontrols to maintain the alignment of the first conformal lateraldeviation symbology with the ILS approach line up until the transitionpoint. In response, the aircraft will follow the ILS approach towardsthe runway. The method further comprises turning the aircraft uponreaching the transition point (620) towards the actual runwaycenterline. At the transition point, the ILS approach line no longerprovides valid information for landing the aircraft on the runway.Therefore, the pilot discontinues aligning the first conformal lateraldeviation symbology with the ILS approach line at the transition point.Instead, the method continues with aligning a second conformal lateraldeviation symbology with an extended runway center line after reachingthe transition point (630). The second conformal lateral deviationsymbology indicates to the pilot the degree of the aircraft's lateraldeviation from the extended runway center line. The pilot maneuvers theaircraft's flight controls to maintain the alignment of the secondconformal lateral deviation symbology with the extended runway centerline through completion of the landing. In response, the aircraft willbe properly aligned with the center line of the runway as the aircrafttouches down onto the runway.

Several means are available to implement the graphics generatingprocessor of the current invention. These means include, but are notlimited to, digital computer systems, programmable controllers, or fieldprogrammable gate arrays. Therefore other embodiments of the presentinvention are program instructions resident on computer readable mediawhich when implemented by such controllers, enable the controllers toimplement embodiments of the present invention. Computer readable mediainclude any form of computer memory, including but not limited to punchcards, magnetic disk or tape, any optical data storage system, flashread only memory (ROM), non-volatile ROM, programmable ROM (PROM),erasable-programmable ROM (E-PROM), random access memory (RAM), or anyother form of permanent, semi-permanent, or temporary memory storagesystem or device. Program instructions include, but are not limited tocomputer-executable instructions executed by computer system processorsand hardware description languages such as Very High Speed IntegratedCircuit (VHSIC) Hardware Description Language (VHDL).

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

1. A graphical display system for an aircraft, the system comprising: aprocessor adapted to perform real-time computations necessary forgenerating graphical representations of the aircraft's position, whereinthe processor is further adapted to generate a first conformal lateraldeviation symbology representing the aircraft's current position withrespect to an approach line, and generate a second conformal lateraldeviation symbology representing the aircraft's current position withrespect to an extended runway center line; a runway assistance landingsystem receiver coupled to the processor, the runway assistance landingsystem receiver adapted to receive signals for the processor transmittedby an airport runway assistance landing system; one or more aircraftposition sensors coupled to the processor, the sensors adapted to detectthe position of the aircraft; a display coupled to the processor, thedisplay adapted to display the graphical representations generated bythe processor; one or more terrain databases coupled to the processor,the one or more terrain databases adapted to provide the processor withdata necessary to generate accurate graphical representations of theterrain in the proximity of the aircraft; and one or more flightmanagement system databases coupled to the processor, the one or moreflight management system databases adapted to provide the processor withdata necessary to generate accurate graphical representations of one ormore of airport runways, airport runway centerlines, and runwayassistance landing system beacon positions.
 2. The system of claim 1,wherein the display further comprises one or more of a head-downdisplay, a flat panel video display, a picture tube video display and ahead-up display.
 3. The system of claim 1, wherein the one or moreaircraft position sensors include one or more of a global positioningsystem unit and an inertial navigation system.
 4. The system of claim 1,wherein the approach line is based on ILS signals received from anairport.
 5. The system of claim 1, wherein the extended runwaycenterline is based on one or both of runway end centerpoint locationsstored in the one or more flight management system databases and runwayend centerpoint locations uplinked from a local airport transmitter. 6.The system of claim 1, wherein the intersection of the approach line andthe extended runway centerline indicate a transition point indicatingwhere a pilot of the aircraft should turn in order to align the aircraftfor landing on the offset runway.
 7. The system of claim 1, wherein theprocessor is adapted to detect when the aircraft is approaching anoffset runway by comparing runway direction data obtained from the oneor more flight management system databases with approach line dataobtained from the runway assistance landing system.
 8. The system ofclaim 1, wherein the processor is adapted to determine when the aircraftis approaching an offset runway based on runway direction data uplinkedfrom an airport transmitter
 9. The system of claim 1, wherein theprocessor is further adapted to display an extended runway centerlineand an approach line upon manual activation.
 10. The system of claim 1,wherein the processor is further adapted to calibrate the position andorientation of the approach line with respect to one or more of, theaircraft's current position, a runway's position, and a runwayassistance landing system beacon position.
 11. A method for displayinglateral deviation symbology in offset approaches, the method comprising:displaying an extended runway center line; and displaying an approachline.
 12. The method of claim 11, wherein the approach line is an ILSapproach line.
 13. The method of claim 11 further comprising: displayinga first conformal lateral deviation symbology with respect to theapproach line during an approach prior to reaching a transition point;and displaying a second conformal lateral deviation symbology withrespect to the extended runway center line during an approach afterreaching the transition point.
 14. The method of claim 13 wherein thefirst conformal lateral deviation symbology is distinguishable from thesecond conformal lateral deviation symbology.
 15. The method of claim 14wherein the first conformal lateral deviation symbology isdifferentiated from the second conformal lateral deviation symbology byone or more of a different color, a different line thickness, or adifferent line style.
 16. The method of claim 11 wherein the extendedrunway center line is a different color from the approach line.
 17. Themethod of claim 11 further comprising: indicating a transition point byending the approach line at a point where the approach line intersectsthe extended runway center line.
 18. The method of claim 11 furthercomprising: ceasing the display of the approach line during and approachafter reaching a transition point.
 19. A method for landing an aircraftat an airport runway having an offset approach, the method comprising:aligning a first conformal lateral deviation symbology with an approachline during an approach prior to reaching a transition point; turningthe aircraft upon reaching the transition point; and aligning a secondconformal lateral deviation symbology with an extended runway centerline during an approach after reaching the transition point.
 20. Themethod of claim 19, wherein the approach line is an ILS approach line.21. A system for on-aircraft display of lateral deviation symbology foruse in offset approaches, the system comprising: means for generating aconformal video display representation of an aircraft's currentposition; means for notifying a flight crew of the existence of anoffset approach; means for displaying an extended runway center line;and means for displaying an approach line.
 22. The system of claim 21,wherein the approach line is an ILS approach line.
 23. The system ofclaim 21 further comprising: means for displaying a first conformallateral deviation symbology with respect to the approach line during anapproach prior to reaching a transition point.
 24. The system of claim21 further comprising: means for displaying a second conformal lateraldeviation symbology with respect to the extended runway center lineduring an approach after reaching the transition point.
 25. The systemof claim 21 further comprising: means for detecting an offset runway.26. The system of claim 21 further comprising: means for comparingrunway direction data with approach line data obtained from runwayassistance landing system signals.
 27. A computer-readable medium havingcomputer-executable program instructions for a method for displayinglateral deviation symbology in offset approaches, the method comprising:notifying a flight crew of the existence of an offset approach;displaying an extended runway center line; and displaying an approachline.
 28. The computer-readable medium of claim 27, the method furthercomprising: displaying a first conformal lateral deviation symbologywith respect to the approach line during an approach prior to reaching atransition point; and displaying a second conformal lateral deviationsymbology with respect to the extended runway center line during anapproach after reaching the transition point.
 29. The computer-readablemedium of claim 28 wherein the first conformal lateral deviationsymbology is distinguishable from the second conformal lateral deviationsymbology.
 30. The computer-readable medium of claim 29 wherein thefirst conformal lateral deviation symbology is differentiated from thesecond conformal lateral deviation symbology by one or more of adifferent color, a different line thickness, or a different line style.31. The computer-readable medium of claim 27, wherein the extendedrunway center line is a different color from the approach line.
 32. Thecomputer-readable medium of claim 27, the method further comprising:indicating a transition point by ending the approach line at a pointwhere the approach line intersects the extended runway center line. 33.The computer-readable medium of claim 27, the method further comprising:ceasing the display of the approach line during and approach afterreaching a transition point.
 34. The computer-readable medium of claim27 wherein the approach line is an ILS approach line.
 35. A graphicaldisplay system for an aircraft, the system comprising: a processoradapted to perform real-time computations necessary for generatinggraphical representations of the aircraft's position, wherein theprocessor is further adapted to generate a first lateral deviationsymbology representing the aircraft's current position with respect toan approach line, and generate a second lateral deviation symbologyrepresenting the aircrafts current position with respect to an extendedrunway center line; a runway assistance landing system receiver coupledto the processor, the runway assistance landing system receiver adaptedto receive signals for the processor transmitted by an airport runwayassistance landing system; one or more aircraft position sensors coupledto the processor, the sensors adapted to detect the position of theaircraft; and a display coupled to the processor, the display adapted todisplay the graphical representations generated by the processor. 36.The system of claim 35, wherein the display further comprises one ormore of a head-down display, a flat panel video display, a picture tubevideo display and a head-up display.
 37. The system of claim 35 furthercomprising: one or more databases coupled to the processor, the one ormore databases adapted to provide the processor with data necessary togenerate accurate graphical representations of one or both of theterrain in the proximity of the aircraft and airport runways and airportrunway centerlines.
 38. The system of claim 37, wherein the processor isadapted to detect when the aircraft is approaching an offset runway bycomparing runway direction data obtained from the one or more databaseswith approach line data obtained from the runway assistance landingsystem.
 39. The system of claim 37, wherein the processor is furtheradapted to determine when the aircraft is approaching an offset runwaybased on runway direction data uplinked from an airport transmitter 40.The system of claim 35, wherein the processor is further adapted todisplay a first conformal lateral deviation symbology with respect tothe approach line during an approach prior to reaching a transitionpoint, and display a second conformal lateral deviation symbology withrespect to the extended runway center line during an approach afterreaching the transition point.
 41. The system of claim 35, wherein theprocessor is further adapted to uplink data necessary to generateaccurate graphical representations of one or more of airport runways,airport runway centerlines, and runway assistance landing system beaconpositions.
 42. The system of claim 35, wherein the processor is furtheradapted to calibrate the position and orientation of the approach linewith respect to one or more of, the aircraft's current position, arunway's position, and a runway assistance landing system beaconposition.